In offset lithography, an image is present on a printing plate as a pattern or “image” of ink-accepting (oleophilic) and ink-repellent (oleophobic) surface areas. In a typical sheet-fed offset press system, the imaged plate is mounted to a plate cylinder, where it is inked. The plate is then brought into contact with the compliant surface of a blanket cylinder. The blanket cylinder, in turn, applies the image to paper sheets which are brought into contact with the blanket cylinder by an impression cylinder. Although the plates for offset presses were traditionally imaged photographically, more recently, a number of electronic alternatives have been developed for placing the image onto the plate. These digitally controlled imaging devices include lasers that chemically alter or destroy one or more plate layers, ink jets that directly deposit ink-repellent or ink-accepting spots on a plate blank and spark or ion discharge devices which physically alter the topology of the plate blank. These various imaging approaches are described in detail in U.S. Pat. Nos. 3,506,779; 4,054,094; 4,347,785; 4,911,075 and 5,385,092, among others.  
Plates can be imaged on-press or, more traditionally, on an off-press platesetter. A digitally operated platesetter includes an imaging cylinder to which the plate is initially mounted, and which carries the plate past the head of the imaging device. That device transfers the image to the plate. The imaged plate is then removed from the platesetter and transferred to the plate cylinder of the printing press. Whenever a plate is mounted to a cylinder (either on a press or on a platesetter), it is essential that the leading and trailing edges of the plate be secured firmly to the cylinder and that the plate be wrapped tightly around the cylinder. This ensures that there will be no relative movement between the plate and the cylinder when the cylinder is rotated, as well as overall uniformity of imaging. 
One condition that can interfere with smooth, consistent contact between the plate and the cylinder is plate expansion caused by temperature differentials. A printing plate is typically a multilayer construction including, for example, polymeric and metal layers, and is therefore subject to thermally induced expansion. A plate cylinder or, especially, a platesetter's imaging cylinder that may run numerous successive jobs, can become hotter than the surrounding environment. As a result, when a plate at room temperature encounters the cylinder, it expands. As the plate is wrapped around the cylinder, this expansion occurs progressively, affecting different areas of the plate at different times and leading to mechanical distortions. For example, a traditional sheet-form plate is loaded by first securing its leading edge to the cylinder using a clamp. The cylinder is rotated with the plate under tension in order to ensure tight contact against the cylinder. This tight contact, however, while essential to avoid slippage during imaging (and, especially, during printing), actually prevents dimensional expansion of  the plate. As a result, the plate puckers, creating an uneven surface that interferes with the imaging process (and can lead, for example, to blurred images or even deleterious contact with the imaging head) and potentially with subsequent printing as well. 